Reuseable medical devices generally require disinfection or sterilization between uses. One way to sterilize a reuseable medical device is to expose the device to steam at high temperatures and pressures, i.e. autoclaving. This method, however, is often unsuitable for delicate medical apparatus, such as endoscopes, which may include components that are not heat-resistant. As an alternative, organic sterilizing/disinfecting solutions, such as glutaraldehyde, have been used at ambient temperatures. Glutaraldehyde, however, has limited sterilizing/disinfecting activity and may also cause allergic reactions in patients. Another alternative has been oxidizing sterilizing/disinfecting solutions, such as peracetic acid, hypochlorous acid, or chlorine dioxide. One way to prepare such oxidizing solutions has been through electrochemical processing of aqueous salt solutions as described, for example, in GB 2316090. These oxidizing solutions, such as STERILOX™, are produced by electrochemical cells comprising an anode chamber and a cathode chamber separated by a semi-permeable membrane and include oxidized chlorine species such as hypochlorous acid as sterilizing agents. Such solutions are highly effective in their sterilizing action, but are more aggressive than glultaraldehyde, for example, and may attack the plastic and similar components of medical devices.
The flexible sections of many reusable medical devices, such as endoscopes, are typically provided with polyurethane-based coatings to provide a protective coating and improve the handling properties of the medical device. However, many polyester- or polyether-based polyurethanes are not sufficiently resistant to degradation by oxidizing agents used as sterilants.
One approach to protect this protective coating is by providing an internal vapor barrier layer between the external polyurethane coating and the inner components, such as the optic fibers of an endoscope. (See U.S. Pat. No. 5,876,331). The endoscope may be sterilized by an oxidizing solution in the vapor phase, with the internal vapor barrier layer serving to keep the sterilizing vapor away from lubricants which may be provided in the inner components of the endoscope since a chemical reaction therebetween may otherwise form acids which could attack the polyurethane outer coating. Another approach to protecting the outer coating of a medical device is applying a urethane-silicone copolymer layer to the outer surface of the medical device. (See Japanese Application No. 9-305814 published as No. 11-137510). Such a coating comprises a mixture of a silicone resin and an aliphatic urethane polymer and an aromatic urethane polymer. However, the resistance of this material to hypochlorous acid-based disinfectants has not been found to be adequate.
Therefore, a need exists for protecting the outer coating of an insertable medical device from degradation by a sterilizing solution while maintaining the handling properties of the medical device.